Actuation systems, e.g. rotation ball screw type actuators for adjusting surfaces on an aircraft, generally have high rotational energy due to high motor operating speeds. These systems usually are incapable of sustaining the loading resulting from engaging hard stops, for example jaw/dog stops, at full system rates. Two approaches have been used to circumvent this problem. One method is to provide a sufficiently soft spring rate at the dog stops to reduce the inertia loading. The spring rate method, however, due to some system configurations may not provide the lightest weight system.
Another method is to use a gradually applied brake as the stop mechanism. Brake stops that are engaged by a mechanism contained within the actuation system may be difficult to release. The inertia energy dissipated in the brake stop may result in locking the brake and preventing the continued operation of the system. In an attempt to eliminate this problem, it is known from U.S. Pat. No. 4,667,779, for example, to employ a one-way clutch which results in a unidirectional brake stop. The use of dual high and low efficiency screw threads to eliminate this problem has also been proposed as in U.S. Pat. No. 4,064,981.
An energy absorbing bidirectional rachet no-back apparatus is disclosed in U.S. Pat. No. 4,480,733. The disclosed apparatus includes in combination a fixed support, a rotatable input member and a rotatable output member. A planetary gear friction couples the output shaft through a ring gear, and compound planet gears on a carrier, including also a ball-ramp torque limiter actuator. No-back mechanisms are also known from U.S. Pat. Nos. 4,834,225 and 4,697,672. These no-back apparatus of the prior art are designed to prevent driven loads from back driving a system if the system motors are inoperative. They do not stop motor operation based on system output position.
U.S. Pat. No. 4,545,470 is directed to a narrow tolerance range slip clutch which controls the amount of torque transmitted between two rotating shafts. The clutch does not stop or prevent rotation of either shaft based on shaft position. U.S. Pat. No. 4,693,349 discloses a torque limiting apparatus which restricts the amount of load a mechanism may encounter due to the system motors. Systems utilizing these components are subjected to inertia spike loads associated with the relatively sudden engagement of these load limiting mechanisms. U.S. Pat. No. 4,458,789 discloses a brake assembly for a multi-disc brake including a force multiplying device. The pneumatically actuated disc brake uses ball-ramps for force multiplying. U.S. Pat. No. 4,750,593 is directed to a disc brake for service combined with parking operation. The disc brake employs a ball-ramp mechanism for actuating the brake.